1. Technical Field
This invention relates to a film transporting system adapted to ascertain that a photographic camera has a film roll loaded therein before the system transports the film roll.
2. Prior Art
Photographic cameras of various types requiring neither skill nor experience of users have become very popular. With these handy prior art cameras, upon closure of the rear cover after a film cartridge has been loaded into the camera, the built-in electric motor is actuated to transport the film roll by a sufficient amount to bring the camera to a state ready for photographing. Immediately after the first release, the motor is actuated again to advance the film roll by one frame and thereby to align the next frame with the aperture. Use of the final frame causes the motor to rewind the film roll into the cartridge.
If the motor is actuated upon depression of the release button for a predetermined period, even though the camera has no film roll loaded therein, the source battery will be rapidly consumed. To solve this problem, it is well known to provide the camera, including the film transporting system adapted to selectively advance and rewind the film roll, with a film existence detector.
In such prior art arrangements, as will be apparent from FIG. 4 of the accompanying drawings, a motor drive signal is applied from central processing unit (CPU) 1 provided in the camera to the film transporter 2 which comprises a motor drive circuit 2a and an electric motor 2b driven by said motor drive circuit 2a. Said CPU 1 is electrically connected to a film travel detector means 3 so that film travel signals are exchanged between said CPU 1 and said film travel detector means 3, which represent an initial advance of the film roll occurring immediately after the film roll has been loaded into the camera; advance of each frame; and rewinding of the film roll taking place immediately after the final frame has been used. A detection signal is applied from a film existence detector 4 to said CPU 1 utilizing DX codes or the like to detect whether the camera has the film roll loaded therein. There is further provided counter 5 adapted to count the number of used frames so that a count signal representing the number of used frames is exchanged between the counter 5 and the CPU 1.
The motor drive signal is applied from the CPU 1 to the film transporter 2 only when the signal representing the existence of the film roll is applied from the film existence detector 4 to the CPU 1.
However, such film transporting system of the prior art has been disadvantageous in that, if the film existence detector 4 erroneously provides the signal indicating the absence of the film roll, due to any failure, the film transporter 2 will not be actuated and the film roll cannot be advanced, although the camera really has the film roll loaded therein. Once the film transporter 2 has been disabled, the operation of film rewinding will be impossible and the camera itself will be disabled. In addition, the user will mistakenly believe that the camera contains no film roll and open the rear cover, resulting in exposure of used film.